A Model Of 6-10 kV Power Three-Core Cable For The Research Of ITS Heating-Up In Normal And Emergency Operating Modes

Abstract

One of the most significant consequences of short circuits and single phase to earth faults in 6-10 kV cable networks is cable insulation heating, which provides its further deflagration and damage of neighboring power supply systems’ elements, which steps up consequential injury. Cable lines overheating during current overload leads to rapid insulation deterioration and cable lines damage rate increasing; similarly, cable heating during single phase to earth faults leads to its transformation to phase-to-phase short circuit, which requires faulted cable line emergency shutdown by relay protection devices operation and, moreover, can aid in cable deflagration when it is installed inside cable tunnels. Reference documents contain several calculation methods for cable line temperature definition both in steady-state and transient modes [1,2]. The main disadvantages of these methods are sufficiently restricted application sphere (only for symmetrical modes) and impossibility for accurate records of thermal conductivity and other thermophysical and geometric parameters of the researched cable line and external environment (soil, air, etc). For the solution of this problem an approach, which was described by F.H. Van Wormer in the 1950s [3] and also mentioned in [4–6], exists. According to this approach, the heated cable line and external environment are presented in the form of equivalent RC-branches, which simulates the process of transition and accumulation of heat. Nevertheless, during composition of such models an issue of computational space size and appropriate sampling rate of elementary RC-branches definition occurs. The model of cable line and external environment on the basis of so-called “Markov’s chains” [for example, 5] is also the case of interest, because it will allow to research qualitative characteristics of the system “cable line – the external environment” in the context of its electromagnetic heating. The main goal of this research is to compile a digital model of 6–10 kV three-core cable line for the definition of qualitative characteristics of the system “cable line – the external environment” as the object, which is exposed to thermal effect and the research of cable and soil temperature dependence on different factors.